A Brief History of Microbiology

A Brief History of Microbiology
Chapter 1 A Brief History of Microbiology

“We used to see from the elephant down to the mite; thenceforth we had a world populated with tiny animalcules to whom the mite was elephant.” -F. Gonzales-Crussi

The Early Years of Microbiology
What Does Life Really Look Like? Antoni van Leeuwenhoek (Dutch, late 1600s) Began making and using simple microscopes Often made a new microscope for each specimen Examined water and visualized tiny animals, fungi, algae, and single-celled protozoa: “animalcules” By end of 19th century, these organisms were called microorganisms © 2012 Pearson Education Inc. 3

Figure 1.1 Antoni van Leeuwenhoek

Figure 1.2 Reproduction of Leeuwenhoek’s microscope
Lens Specimen holder

How Can Microbes Be Classified? Carolus Linnaeus developed taxonomic system for grouping similar organisms together Leeuwenhoek’s microorganisms grouped into six categories: Bacteria Archaea Fungi Protozoa Algae Small multicellular animals © 2012 Pearson Education Inc. 6

Classification 3 Domains: Domain Bacteria Domain Archaea
Domain Eukarya 4 Kingdoms Kingdom Animalia Kingdom Plantae Kingdom Fungi Kingdom Protista

Bacteria and Archaea Unicellular and lack nuclei Much smaller than eukaryotes Found everywhere there is sufficient moisture Reproduce asexually Two kinds Bacteria – cell walls contain peptidoglycan Archaea – cell walls composed of polymers other than peptidoglycan © 2012 Pearson Education Inc. 9

Figure 1.4 Cells of the bacterium Streptococcus
Prokaryotic bacterial cells Nucleus of eukaryotic cheek cell

Fungi Eukaryotic (have membrane-bound nucleus) Obtain food from other organisms Possess cell walls Include Molds – multicellular; grow as long filaments; reproduce by sexual and asexual spores Yeasts – unicellular; reproduce by budding or sexual spores © 2012 Pearson Education Inc. 11

Figure 1.5 Fungi-overview

Protozoa Single-celled eukaryotes in kingdom Protista. Similar to animals in nutrient needs and cellular structure Live freely in water; some live in animal hosts Asexual (most) and sexual reproduction Most are capable of locomotion by Pseudopodia Cilia Flagella © 2012 Pearson Education Inc. 13

Figure 1.6 Locomotive structures of protozoa-overview

Algae Unicellular or multicellular Photosynthetic Simple reproductive structures Categorized on the basis of pigmentation, storage products, and composition of cell wall © 2012 Pearson Education Inc. 15

Figure 1.7 Algae-overview

Figure 1.8 An immature stage of a parasitic worm in blood
Red blood cell

Figure 1.9 Viruses infecting a bacterium
Viruses assembling inside cell

The Golden Age of Microbiology
Scientists searched for answers to four questions Is spontaneous generation of microbial life possible? What causes fermentation? What causes disease? How can we prevent infection and disease? © 2012 Pearson Education Inc. 19

Some thought living things arose from three processes Asexual reproduction Sexual reproduction Nonliving matter Aristotle proposed spontaneous generation Living things can arise from nonliving matter © 2012 Pearson Education Inc. 20

Redi’s Experiments When decaying meat was kept isolated from flies, maggots never developed Meat exposed to flies was soon infested As a result, scientists began to doubt Aristotle’s theory © 2012 Pearson Education Inc. 21

Figure 1.10 Redi’s experiments
Flask unsealed Flask sealed Flask covered with gauze

Needham’s Experiments Scientists now thought microbes, but not animals, could arise spontaneously Needham’s experiments reinforced this idea He boiled flasks of gravy and corked them. Microorganisms were later found to be in the gravy, demonstrating spontaneous generation. © 2012 Pearson Education Inc. 23

Spallanzani’s ( ) Experiments Conclusions Needham failed to heat vials sufficiently to kill all microbes and had not sealed vials tightly enough Microorganisms exist in air and can contaminate experiments Spontaneous generation does not occur Critics argued against Spallanzani’s experiments Sealed vials did not allow enough air for organisms to survive Prolonged heating destroyed “life force” Spallanzani heated the flasks and sealed the glass with the flame so that nothing could get in. He heated one flask for a few minutes and another for an hour. He also prepared an identical set which he stoppered with cork. When he observed the broth under the microscope, he discovered that microorganisms contaminated every one but the one that had been boiled for an hour. © 2012 Pearson Education Inc. 24

Figure Louis Pasteur

Pasteur’s ( ) Experiments When the “swan-necked” flasks remained upright, no microbial growth appeared When the flask was tilted, dust from the bend in the neck seeped back into the flask and made the infusion cloudy with microbes within a day © 2012 Pearson Education Inc. 26

Figure 1.12 Pasteur’s experiments with “swan-necked” flasks
Steam escapes from open end of flask. Dust from air settles in bend. Air moves in and out of flask. Months Infusion is heated. Infusion sits; no microbes appear. Infusion remains sterile indefinitely.

The Scientific Method Spontaneous generation debate led in part to scientific method Observation leads to question Question generates hypothesis Hypothesis is tested through experiment(s) Results prove or disprove hypothesis Accepted hypothesis leads to theory/law Reject or modify hypothesis © 2012 Pearson Education Inc. 28

Figure 1.13 The scientific method
Observations Question Repeat Experimental data support hypothesis Accept hypothesis Theory or law Experiment, including control groups Hypothesis Observations Reject hypothesis Experimental data do not support hypothesis Modify hypothesis Modified hypothesis

What Causes Fermentation? Spoiled wine threatened livelihood of vintners Some believed air caused fermentation Others insisted living organisms caused fermentation Vintners funded research to prevent spoilage during fermentation This debate also linked to debate over spontaneous generation © 2012 Pearson Education Inc. 30

Figure 1.14 Pasteur's application of the scientific method
Observation: Fermenting grape juice Microscopic analysis shows juice contains yeasts and bacteria. Hypothesis Experiment Observation Conclusion Day 1: Flasks of grape juice are heated sufficiently to kill all microbes. Day 2 I. Spontaneous fermentation occurs. No fermentation; juice remains free of microbes Reject hypothesis I. Flask is sealed. II. Air ferments grape juice. No fermentation; juice remains free of microbes Reject hypothesis II. Flask remains open to air via curved neck. III. Bacteria ferment grape juice into alcohol. Bacteria reproduce; acids are produced. Modify hypothesis III; bacteria ferment grape juice into acids. Juice in flask is inoculated with bacteria and sealed. IV. Yeasts ferment grape juice into alcohol. Yeasts reproduce; alcohol is produced. Accept hypothesis IV; yeasts ferment grape juice into alcohol. Juice in flask is inoculated with yeast and sealed.

Table 1.1 Some Industrial Uses of Microbes

What Causes Disease? Pasteur developed germ theory of disease Robert Koch ( ) studied causative agents of disease Anthrax Also determined that anthrax can form endospores that allow them to survive harsh conditions. Examined colonies of microorganisms growing on potatoes—pure cultures. Discovered the causative agent of tuberculosis. © 2012 Pearson Education Inc. 33

Figure Robert Koch

Figure 1.16 Bacterial colonies on agar
Bacterium 6 Bacterium 7 Bacterium 5 Bacterium 8 Bacterium 4 Bacterium 9 Bacterium 3 Bacterium 10 Bacterium 2 Bacterium 11 Bacterium 1 Bacterium 12

Koch’s Postulates Suspected causative agent must be found in every case of the disease and be absent from healthy hosts Agent must be isolated and grown outside the host When agent is introduced into a healthy, susceptible host, the host must get the disease Same agent must be found in the diseased experimental host © 2012 Pearson Education Inc. 37

How Can We Prevent Infection and Disease? Semmelweis and handwashing Ignaz Semmelweis required medical students to wash their hands between procedures, greatly reducing the incidence of women contracting puerperal fever during childbirth. Lister’s antiseptic technique First to use antiseptics during surgery. © 2012 Pearson Education Inc. 38

How Can We Prevent Infection and Disease?
Nightingale and nursing Florence Nightingale was a nurse who emphasized cleanliness in hospitals. Snow – infection control and epidemiology Jenner’s vaccine – field of immunology Edward Jenner developed the first vaccine. It was for smallpox

John Snow (1813-1858) and cholera
John Snow is considered the father of epidemiology. He went door to door in London and realized that people who were contracting cholera were getting their water from a contaminated source and he eventually convinced city officials to remove the handle from the pump, which helped end the cholera epidemic.

Two competing theories
Miasma Theory Germ Theory Most people and scientists held to this. Disease is caused by “bad air.” Took a while to be accepted.

John Snow’s map John Snow went house to house and interviewed people about their water-drinking habits. He discovered that the majority of the deaths came from people who had drunk from the Broad Street pump, which was supplied by a different water company than a nearby pump. The water was being contaminated with sewage. This led to the development of a sewer system in London.

Guess what this is.

Vibrio cholerae Causative agent was isolated by Robert Koch in 1883. He actually wasn’t the first to isolate it, but he received credit for it.

“We must learn to shoot microbes with magic bullets.”
Paul Ehrlich “We must learn to shoot microbes with magic bullets.” Developed the first chemotherapeutic agent. It was called salvarsan and was used to treat syphilis. Ehrlich spent considerable time developing compounds before he found one that was effective against syphillis.

Paul Ehrlich Ehrlich began his work studying various dyes. He was pals with Robert Koch and showed Koch how to stain the bacteria that causes tuberculosis.

The Modern Age of Microbiology
The “Golden Age of Microbiology” yielded many important discoveries and opened several new fields such as immunology, epidemiology, chemotherapy, and genetic engineering. Scientists had a grand hope that they would be able to eliminate microbial disease. This has proven more difficult than previously thought. Why?

Fungus colony (Penicillium)
Figure Effects of penicillin on a bacterial “lawn” in a petri dish Fungus colony (Penicillium) Zone of inhibition Bacterial colonies (Staphylococcus)

A Brief History of Microbiology

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